2.1 The dangers of infection from accidental contact with the pointed end of used hypodermic needles has long been recognized and is well documented. For example, refer to Jagger, Hunt, Brand-Elnaggar and Pearson, the New England Journal of Medicine, August, 1988. In most procedures, the greatest avoidable risk of accidental needle puncture, or "needle-stick", occurs during handling of the used needle, when it is generally inserted into a protective sheath for disposal. This action usually requires moving the hand which holds the sheath towards the pointed tip of the needle, and any inaccuracy in this operation raises the possibility of a puncture. The risk of this is greatly increased if the operator is working under stress, such as time-pressure or fatigue, or is handicapped by marginal eyesight or unsteady hands.
2.2 A number of devices have been developed to deal with the general problem of needle-sticks, and reference may be made to U.S. Pat. Nos. 4,747,835 (Sandhaus); 4,735,618 (Hagen); 4,735,617 (Nelson, Fieme); 4,731,059 (Wanderer, Sagsfretter); 4,725,267 (Vaillancourt); 4,720,285 (Pickhard); 4,623,336 (Pedicano, Kane); 4,430,082 (Schwabacher, et el), and 4,755,170 (Golden).
2.3 Some of these, for example Sandhaas, Neison/Flome, and Pedicano/Kane, provide an enlarged conical entry to the protective sheath, so that the resulting larger target reduces the chance of the operator missing the entry. This may be combined with some non-manual means of holding the sheath assembly, further reducing the risk. All of these devices require the operator to divert his attention from his immediate task and to exercise some measure of care in placing the needle into the sheathing device.
2.4 Others of these, for example Hagen and Vaillancourt, aspire to attain the desirable goal of keeping the hands wholly behind the sharpened tip of the needle during the manipulation of the protective device. The Hagen design stores the tip protector around the base of the needle, but in this mode the lateral retaining members are folded in an "arms akimbo" configuration, mending to either side of the needle in a manner which could interfere with the proper manipulation of the syringe and needle during insertion and removal. The Vaillancourt design mounts the tip protector at the distal end of a cylindrical bellows coaxial with the needle, which may be collapsed longitudinally to allow storage of the tip protector at the needle base. This is more compact, but requires care and attention during the needle sheathing action to ensure that the needle is properly located within the protector. Failure to do this could result in the needle becoming exposed again. Both designs appear to offer uncertainty of protection in the event of an impact against the tip of the needle, such as might occur if the latter were dropped. As both designs appear to employ flexed plastic or elastomeric joints or folds for their articulation, operation of the device might encounter significant stiffness, depending upon the desired mechanical strength of this articulation and the length of time over which the device was kept in the stored position prior to use.
2.5 Golden provides for a sealing cover to be placed over a needle tip after being slid down the needle from the base. This tip, made of absorbent material that is not normally stored on the needle prior to use, is not of a dimension that would fit conveniently within a storage cover. The positioning of this cover is either by means of eye judgment, relying on a marker on the needle; or by means of a thickened portion formed near the tip of a specially configured needle. This cover does not, however, fasten, clamp or lock onto the needle tip in any way. A needle-stick injury could simply occur by the accidental withdrawal of the cover from the tip.
2.6 Against this background, it is the object of this invention to provide a protective guard for hypodermic needles with the following useful functions:
2.6.1 It provides a protective guard which forms an integral part of the needle assembly and which is dimensionally shorter in length than the needle.
2.6.2 The protective guard may be stored prior to use at the base of the needle shaft in a manner which requires a minimum of space and is substantially unobtrusive.
2.6.3 The protective guard may be retained in its storage position by a retention means which allows the ready release of the protective device when it is to be moved into its protecting position.
2.6.4 The protective guard may be moved into its protecting position on the needle; tip following needle use in a way which requires no significant training, no manual skills, no visual acuity, or particular level of lighting.
2.6.5 The protective guard may be moved into its protecting position with the hands always behind the needle tip and with the motion of the hands always directed safely away from the needle tip.
2.6.6 The protective guard automatically detects the needle tip to establish its correct protecting position on the needle shaft with no judgement required of the operator.
2.6.7 The protective guard automatically locks itself to the needle shaft with no additional action required of the operator when it has reached the correct axial protecting position.
2.6.8 According to one further arrangement when the protective guard is locked in its protecting position the sharp tip of the needle is automatically covered by a substantial thickness of material to provide a high degree of protection against re-emergence of the needle tip from the protective cover.
2.6.9 When the protective guard is in its protecting position it presents a smooth, substantially unobtrusive surface with no protrusions.
2.6.10 When the protecting guard is in its protecting position the used needle may be handled and disposed of with no more than normal handling precautions than are customary for potentially contaminated medical materials.
2.6.11 When the protecting guard is used in association with an insertion needle within a catheter, the guard is automatically transferred from its storage position to the needle tip by the action of withdrawing the insertion needle from the catheter.
2.7 An important area of concern in the disposal of possibly contaminated needles relates to the use of intravenous catheters. In these devices, the needle is usually supplied in a pre-packaged assembly, already inserted inside a flexible, close-fitting catheter tube, the latter having a base with coupling means to allow the subsequent connection of tubing for intravenous infusion or similar procedures. The needle length is such that its point extends slightly beyond the distal end of the catheter, thus acting as a piercing means to allow insertion of the catheter and needle into a blood vessel in the patient. Thus such needles are known as "insertion needles".
2.8.degree. Following insertion of the needle and catheter, the needle is withdrawn from inside the catheter and must be disposed of. At this point the operator's attention is taken up with other matters, mainly relating to the attachment of tubing to the catheter and controlling loss of blood, and this makes him significantly more vulnerable to needle stick accidents if he must divert his attention to safe disposal of the needle by conventional means.
2.9 By a simple adaptation, the subject protective guard may be attached to the catheter as part of the pre-packaged assembly, with the needle installed first through the guard and then inside the catheter. When the operator withdraws the needle from the catheter after insertion into the patient, the guard remains frictionally attached to the catheter, allowing the needle to slide freely through it in either direction, until the point of the needle is withdrawn inside the body of the guard. At this point the guard locks securely over the tip of the needle, allowing the operator to detach the guard from the catheter by a slight additional withdrawal force. The needle, with the guard in place, may be then disposed of without further attention from the operator.
2.10.degree. In this way, no separate action or thought is required of the operator during the needle withdrawal process, since the guard is automatically applied as the needle point exits the catheter during the normal withdrawal sequence, and therefore no training is required in the use of the guard element.
2.11.degree. These desirable qualities, as well as other features and characteristics are provided by the subject invention, using the arrangements, construction, components, and steps as described and illustrated hereafter in this disclosure, and which exemplify this invention.